I have an unheated darkroom in the basement of the house that is sided by an exposed, above grade wall (the house is built on a slope). As a result, the temperature of my stock solutions on the shelf fluctuate with changes in the darkroom's ambient temperature, especially in winter extremes.

Naturally, the development time of any developer can be lengthened to compensate for solution temperatures that are cooler than the manufacturer's recommended developing temp (usually 68 degrees). I often use Ilford Perceptol as my developer of choice, and page 4 of the 2010 data sheet has a text explanation, as well as a graph, about how much to lengthen the development time by the cooler temperature level. It can be viewed at this link: https://www.ilfordphoto.com/amfile/file/download/file/1829/product/708/ (http://www.ilfordphoto.com/amfile/file/download/file/1829/product/708/)

The text states to "increase the given development times by 10% for each 2 degrees Fharenheit drop in temperature." However, the graph shows amounts that are greater than this.

Take, for example, the time of 6 minutes at 68 degrees (which is not what I use for Perceptol, but it provides an easy reference for illustration purposes). Let's say you wanted to develop the film at 58 degrees, or 10 degrees below the recommended 68 degrees. Using the text formula, that would involve a 50% increase in development time, from 6 to 9 minutes. But if you look at the graph, the 6 minute mark goes to about 10 minutes at 58 degrees. That's a difference of a full minute between the two recommended adjustments.

I thought that either Ilford is comfortable with generalities, or perhaps the 10% increase in time is supposed to be compounded with each 2 degree interval, which would yield about 9 minutes and 40 seconds.

So I have three questions for those interested in responding to any one of them:

What is your take on the technical data sheet?
What has been your experience, if any, with increasing development times for cooler bath temperatures?
What's the coolest temperature you've developed film in?

Thanks!

ic-racer

10-Feb-2019, 20:57

In the 1980s I used a simple software program that I ran on my Atari ST computer to calculate the times just before I poured the developer into the tank. I print on multigrade paper, so small variations in negative gamma don't matter. Since 1999 I use a Jobo, which keeps everything at the same temp.

Alan9940

10-Feb-2019, 21:22

If developing film using hand tanks, I generally use a temp controlled water bath whether hot or cold. If my ambient darkroom temp is 68F, within maybe a degree or two, I don't bother with the water bath. For sheet film, I use a Jobo. Regardless, I try to keep my film processing in the 65-75F range. I have gone as high as 80F, but worrying about being too cold isn't an issue where I live. ;)

Jerry Bodine

10-Feb-2019, 23:17

This Ilford chart complies with compounding the 10% rule, checking it for your example of 6 min @ 68F, but as you can see the chart only goes down to 64F. Maybe that's an implied suggestion to not develop at temp lower than 64F.

The text states to "increase the given development times by 10% for each 2 degrees Fharenheit drop in temperature." However, the graph shows amounts that are greater than this.

Hello Mike,

You should be aware that this is a geometric progression, not an arithmetic one. A*5 is not the same than A^5 (A raised to 5)

So, for an easy way, you may make a repetitive calculation for each 2ºF step increase.

Just use that generic table for corrections. Try to do all at 20ºC, if at end of development temp shifted say 1ºC then you may compensate a bit with time. IMHO the table has to be used for that shift, making the process at around 20ºC its easy and this is the good and consistent way, the corrections are good for the case you have a shift during developement

What is your take on the technical data sheet?

Kodak and Fuji datasheets are technically very, very good, Ilford ones are less technically good but still very, very good in practice and easier understand.

Always read datasheets twice, with a "magnifier". Always we may find interesting information.

What has been your experience, if any, with increasing development times for cooler bath temperatures?

As I use Xtol 1:1 I make the mix of stock with tap water that has the right temperature to make end the mix in 20ºC, if stock is at 18 then make tap water at 22, so it ends in 20.

If you have developer at (say) 16ºC you can place it in a tray and put your hand in (I use a glove if developer is not "eco-friend" Xtol). Your hand is at 36ºC and if you move it a bit then soon developer will heat up.

If developer is at 24ºC then use an ice cube in the developer until it cools to 20ºC, it will add little water, an irrelevant amount.

You can always place developer in a beaker, and the beaker in a hot or cold bath, then stirr until you get your temp.

Use only lower temp if development time is too short for a precise process, a under 5 min development is not recommended, as in that situation time inaccuracies have more relative impact, and we may have a less even development.

What's the coolest temperature you've developed film in?

I made low temperature development (16ºC) with very ancient film, to not soften/damage inestable emulsion, with HC-110 because it's low fog in a situation where fog may be a problem.

Regards,
Pere

Pere Casals

11-Feb-2019, 02:04

Maybe that's an implied recommendation to not develop at temp lower 64F.

Perhaps, but also IMHO these are the useful temperatures, not easy that under 18ºC is useful, while we may want 27ºC to shorten a long time from a very diluted developer. So IMHO in general 18 to 27 is what we want to know.

Willie

11-Feb-2019, 07:34

Why not buy an electric heater and get the room to a comfortable temperature before working in it? The radiator type heaters, oil filled, don't put out light or fumes and you can turn it on the day or some time before you will process film and get the chemistry up to temperature so it and you work comfortably.

A few sheets of insulation with something like P2000, a styrofoam board with aluminized mylar on it can be put against the walls. It works well, is lightweight and does not shed dust or fibres like fibreglass will. It is worth looking into for your space.

Keep in mind that hydroquinone, an agent in many developers, loses activity relative to other developing agents at low temperature and increases in activity at higher temperatures at a faster rate than other developing agents (e.g., Metol and Phenidone). In practice, this means that different developers end up with differing temperature/activity coefficients, i.e., the Ilford chart is an average; your specific developer may need more or less compensation.

Best practice, of course, is to find one temperature within the range of activity for your developer and standardize on that. 20°C is lab standard, but there's no reason you couldn't use 19°C or 22°C as long as you are consistent. Choosing one temperature that you can achieve most of the time is the important thing. For those times that temperature has to vary, using the compensation chart will get you in the ballpark, but may not give precisely the same results. If that's good enough, then no problem, but if you need real precision in developing, for whatever reason, then striving for your standard temp is best.

Doremus

Heroique

11-Feb-2019, 13:30

However, the graph shows amounts that are greater than this.

Sometimes, a quick example helps…

For simplicity, let's say for each degree colder, one needs 10% additional development time (a little different than your situation).

1) So, if a given temperature needs 10 minutes, then one degree colder would call for 11 minutes of development time. (10 min. + 10% = 11)

2) And if your temperature is an additional degree colder than that (for a total of two degrees colder), it would be 12.1 minutes. (11 min. + 10% = 12.1)

In other words, two degrees colder doesn't mean 12.0 minutes; it means 12.1 minutes. That's what the chart is trying to say. (Kind of like 10% annual compounding interest in a 401(k) account, great for saving-up for a darkroom in retirement.)

As already mentioned, best is to use charts as a starting point, but over time, record and trust personal results w/ a consistent method – plus a good thermometer and a healthy understanding of its precision vs. accuracy. ;^)

seall

11-Feb-2019, 14:27

Why not buy an electric heater and get the room to a comfortable temperature before working in it? The radiator type heaters, oil filled, don't put out light or fumes and you can turn it on the day or some time before you will process film and get the chemistry up to temperature so it and you work comfortably.

A few sheets of insulation with something like P2000, a styrofoam board with aluminized mylar on it can be put against the walls. It works well, is lightweight and does not shed dust or fibres like fibreglass will. It is worth looking into for your space.

This is similar to what I do, my room heater is set to 22C but when I mix stuff I take it from cold water and bottles then into the room and sit it next to the heater for half an hour or so then go and do something else. Usually by the time I return the liquids in the range of being usable. Sometimes if I am needing stuff heated a bit quicker I sit the liquid directly on top of the heater then turn the bottles once a min.

Give serious thought to a room heater, more than one way to use it and it makes for a better temp to do stuff.

LabRat

11-Feb-2019, 16:15

Keep in mind that hydroquinone, an agent in many developers, loses activity relative to other developing agents at low temperature and increases in activity at higher temperatures at a faster rate than other developing agents (e.g., Metol and Phenidone). In practice, this means that different developers end up with differing temperature/activity coefficients, i.e., the Ilford chart is an average; your specific developer may need more or less compensation.

Best practice, of course, is to find one temperature within the range of activity for your developer and standardize on that. 20°C is lab standard, but there's no reason you couldn't use 19°C or 22°C as long as you are consistent. Choosing one temperature that you can achieve most of the time is the important thing. For those times that temperature has to vary, using the compensation chart will get you in the ballpark, but may not give precisely the same results. If that's good enough, then no problem, but if you need real precision in developing, for whatever reason, then striving for your standard temp is best.

Doremus

+1...

It changes the "look" of your images slightly, as it can affect the scale, granularity, key, tonality, smoothness etc in different ways... If You could compare sheets of film exposed alike of same or different subjects, correctly timed & developed for their respective temps, and you will have negs that will print slightly differently...

This is more noticeable on longer strips of roll
films to the naked eye too as you can spot some differences.... Also sometimes you can notice negs that have been processed in summer or winter at their respective temps, but maybe for different reasons also...

But best to stick to one temp for everything (I think I see a difference and like 67deg, but no developing for me over 72 deg in the hottest of summer)...

YMMV

Steve K

Mike in NY

11-Feb-2019, 17:31

Jerry, Pere, and Heroique, thank you for confirming my “compounding” supposition (or as Pere described it, a geometric rather than arithmetic progression in time).

Doremus and Steve, thank you for letting me know about hydroquinone’s properties at cooler temperatures.

Willie and Seal, I do have a space heater that I turn on in my darkroom, but it typically doesn’t warm up my solutions quickly enough for my satisfaction. But as I think about it… the basement has several different rooms: the darkroom, a photo equipment storage room, and the boiler room. The boiler room is warmer than the other two rooms, so it occurs to me that I could place my stock solutions on a roller cart and keep them in there, and then wheel them into the darkroom when I need them.

Bruce, would you believe I used to have a Zone VI Compensating Developing Timer, but sold it a few years ago when I lived in a house with a climate controlled dark room, and considered it unnecessary.

neil poulsen

12-Feb-2019, 06:34

For me, consistent development is very important. So, I wouldn't mess with any time adjustments. Just develop at your standard temperature. That said, I use a Zone VI compensating developing timer. But, I make sure that my developing temperature is within a degree of 70 degrees. I use the compensating only to adjust time to correct for whatever difference remains.

One can always use a ceramic heater to heat your darkroom before use. There's also the option of keeping your bottled developer, stop, and fixer in a heated space elsewhere than in your darkroom.

Jim Noel

12-Feb-2019, 09:44

I have an unheated darkroom in the basement of the house that is sided by an exposed, above grade wall (the house is built on a slope). As a result, the temperature of my stock solutions on the shelf fluctuate with changes in the darkroom's ambient temperature, especially in winter extremes.

Naturally, the development time of any developer can be lengthened to compensate for solution temperatures that are cooler than the manufacturer's recommended developing temp (usually 68 degrees). I often use Ilford Perceptol as my developer of choice, and page 4 of the 2010 data sheet has a text explanation, as well as a graph, about how much to lengthen the development time by the cooler temperature level. It can be viewed at this link: https://www.ilfordphoto.com/amfile/file/download/file/1829/product/708/ (http://www.ilfordphoto.com/amfile/file/download/file/1829/product/708/)

The text states to "increase the given development times by 10% for each 2 degrees Fharenheit drop in temperature." However, the graph shows amounts that are greater than this.

Take, for example, the time of 6 minutes at 68 degrees (which is not what I use for Perceptol, but it provides an easy reference for illustration purposes). Let's say you wanted to develop the film at 58 degrees, or 10 degrees below the recommended 68 degrees. Using the text formula, that would involve a 50% increase in development time, from 6 to 9 minutes. But if you look at the graph, the 6 minute mark goes to about 10 minutes at 58 degrees. That's a difference of a full minute between the two recommended adjustments.

I thought that either Ilford is comfortable with generalities, or perhaps the 10% increase in time is supposed to be compounded with each 2 degree interval, which would yield about 9 minutes and 40 seconds.

So I have three questions for those interested in responding to any one of them:

What is your take on the technical data sheet?
What has been your experience, if any, with increasing development times for cooler bath temperatures?
What's the coolest temperature you've developed film in?

Thanks!

YOu are adding 10% for the 10 degree difference.YOu need to add 10% for the 1st 2 degrees and then10 % above that total, and so forth. There isa mathematical formula for that which doesn't come to my old mind at the time.

Mike in NY

12-Feb-2019, 09:58

Jim, no, that's not what I did. I added 10% for each two degrees F, for a total of 50% for a ten degree difference. In the example I used, I added an additional 50% of 6 minutes (=3 minutes) to account for a ten degree difference, for a total development time of 9 minutes. But as I mentioned, I suspected a compounding of each 10% increment was needed, and this was confirmed by others, or as Pere clarified, it's a geometric progression in time rather than a linear arithmetic progression.

Doremus Scudder

12-Feb-2019, 12:11

Apropos bringing solutions to temperature. My current darkroom stays at 60°F-62°F in the winter till I get into it (it's built into the slope of a hill a bit, so that it never gets really cold). All the solutions are about that temperature when I arrive. I flip on the lights (they warm up the place a bit), turn up the heater a smidge, set up the trays and get my solutions mixed. I mix with tempered water, so anything mixed fresh is right on.

Anything that's colder than the standard 20°C (68°F) (say saved fix or stop or even print developer from a short session the day before) gets placed into a 2-gallon bucket of hot water. I stir with my thermometer, checking often and remove the solutions when the reach temperature. This is quick. Two liters at 60°F gets up to processing temperature in just a few minutes.

By this time, my 100 sq. ft. darkroom is usually up processing temperature or close enough. For small variations, I use a Zone VI compensating developing timer.

Printing is much less temperature-sensitive than film developing. With the Zone VI timer I don't worry about ambient temperatures in the range from 65°F-72°F. When film developing, I try to get the darkroom within a degree or two of processing temperature. Even closer if I have a large run of film to develop, since drift can be significant over several batches. For just one batch of film (six sheets for me), I don't worry too much. All solutions get mixed to 20°C and poured into their respective trays. These go into a tray one size larger with a water tempering bath also at 20°C. Temperature drift over the developing time is slight with this method, even if the ambient temperature is a few degrees different, and the time in the other solutions not nearly so critical. What is critical is that the film doesn't get a temperature shock. However, since all solutions start at the same temperature, they drift at roughly the same rate so that when I get to transferring film to the stop bath, it has drifted along with the developer and is really close to the same temp. Same with fix and water holding tray. For washing, I make sure my wash water is the same temperature as the last holding tray.

If, for whatever reason, you find you cannot process at one standard temperature, a few things help to maintain consistency.
1. Don't use a hydroquinone-based film developer if you can help. Other developers are less temperature sensitive and, therefore, deliver more consistent results with temperature variation. I use PMK. Pyrocat and Xtol also leap to mind.
2. Use water tempering baths to minimize temperature drift.
3. Standardize on two or three temperatures and use only those, say one for winter, one for summer and 20° for the non-extreme times. Fine-tune your times for the extremes.

Hope this helps,

Doremus

Mike in NY

13-Feb-2019, 12:10

Doremus, that's very useful information - thanks for going into some detail to share it.

JMO

13-Feb-2019, 12:31

Here in the Midwest some of us LFers use electric pig warmer mats to keep print developing trays of the various chemicals at constant temperature (whenever the darkroom is colder than the 21C or 70F). There are no doubt many brands of such pig warmers, but those I've used successfully are made by Kane Mfg., and at their webpage (https://kanemfg.com/products/livestock/hogs/heat-mats-thermostats/) you can see these mats come in a variety of dimensions. Since they are designed for heavy-duty use in farrowing barns by hog raisers, they are totally unaffected by the water and other chemicals that we use in photo darkrooms, and to provide warming temperatures in an appropriate range for DR uses.

The thermostat controller I use is the ESAPCO Model TH-15-HM designed for Corrosive Environments, and this link is to a distributor that sells on-line (http://www.farmtek.com/farm/supplies/ProductDisplay?catalogId=15052&storeId=10001&langId=-1&division=FarmTek&productId=60400). It regulates the temperature of solutions in my enlarging trays to the desired 21C (or whatever one requires), and the whole system (mat and thermostat) is economical and very robust.

In my part of the Upper Midwest there is no concern about my basement becoming too warm in the summer, as the soil temperature about 3-4 feet below ground never gets above “cellar temperature” for wine storage which is 50-55F - so I use the pig warmer mat throughout the year.

Mike in NY

14-Feb-2019, 19:09

JMO, that's pretty darn cool. You should post that information in the "Gear that comes from non-photography sources" at https://www.largeformatphotography.info/forum/showthread.php?149951-Gear-that-comes-from-non-photography-sources